How to break the bottom of a bottle without turning it into smithereens

How to break the bottom of a bottle without turning it into smithereens

Fill an empty beer bottle with water, leaving a small gap at the top. Then firmly hold the bottle by the neck and hit its top with your other hand.

What happens:

The hits create a shock wave of pressure, which breaks the bottom of the bottle exactly at that point, without the slightest damage to the remaining bottle.

Things can travel faster than light....

Things can travel faster than light; and light doesn’t always travel very fast

The speed of light in a vacuum is a constant: 300,000km a second. However, light does not always travel through a vacuum. In water, for example, photons travel at around three-quarters that speed.

In nuclear reactors, some particles are forced up to very high speeds, often within a fraction of the speed of light. If they are passing through an insulating medium that slows light down, they can actually travel faster than the light around them.

When this happens, they cause a blue glow, known as “Cherenkov radiation ”, which is (sort of) comparable to a sonic boom but with light. This is why nuclear reactors glow in the dark.

Incidentally, the slowest light has ever been recorded travelling was 17 meters per second – about 38 miles an hour – through rubidium cooled to almost absolute zero, when it forms a strange state of matter called a Bose-Einstein condensate.

Light has also been brought to a complete stop in the same fashion, but since that wasn't moving at all, we didn't feel we could describe that as "the slowest it has been recorded travelling".

Source:- http://www.telegraph.co.uk/news/science/6546462/The-10-weirdest-physics-facts-from-relativity-to-quantum-physics.html

Colour coding of carbon resistor

Electric field lines and it's properties

Particle That Allows Humans To Live Without Breathing Designed

Scientists have developed a new microparticle filled with oxygen that can be injected into the blood stream, keeping you alive even if you can’t intake air into your lungs. The microparticles are actually tiny capsules (2-4 micrometers tiny) made of a single layer of lipids surrounding a small bubble of oxygen gas. The capsule is suspended in a liquid so that the bubbles don’t get any bigger (which would make them deadly, FYI).

Upon injecting the capsule-filled liquid into the bloodstream, the capsules crash into your red blood cells, transferring the oxygen gas from the capsule to the cell. About 70% of the oxygen injected successfully makes its way into the blood stream this way. This injection method was so successful that the scientists managed to keep rabbits with blocked windpipes alive for fifteen whole minutes.

Source:- http://www.themarysue.com/new-oxygen-particle/

Working of microwave oven.

Microwave oven

It is used to cook the food in a short time. When the oven is operated, the microwaves are generated, which in turn produce a non− uniform oscillating electric field. The water molecules in the food which are the electric dipoles are excited by an oscillating torque. The frequency of oscillating electric field is set at 3GHz which is the natural frequency of oscillation of water molecule. So resonance occurs and water molecules start oscillating with larger amplitude. Hence few bonds in the water molecules are broken, and heat energy is produced. This is used to cook food evenly.

Electrostatic shielding

It is the process of isolating a certain region of space from external field. It is based on the fact that electric field inside a conductor is zero.

During a thunder accompanied by lightning, it is safer to sit inside a bus than in open ground or under a tree. The metal body of the bus provides electrostatic shielding, where the electric field is zero. During lightning the electric discharge passes through the body of the bus.

Danger signals are red. Why?

The reason why the color red is used for danger signals is that red light is scattered the least by air molecules. The effect of scattering is inversely related to the fourth power of the wavelength of a color. Therefore blue which has the least wavelength of all the visible radiations is scattered the most and red which has the highest wavelength is scattered the least.
So red light is able to travel the longest distance through fog, rain, and the alike.

Electric dipole and electric dipole moment.

Electrical Charge and it's properties.

Charge is the fundamental property of a material body due to which electrical forces arises.

When a piece of amber is rubbed with fur, it acquires the property of attracting light objects like bits of paper.

In the 17th  century, William Gilbert discovered that, glass, ebonite etc, also exhibit this property, when rubbed with suitable materials. The substances which acquire charges on rubbing are said to be ‘electrified’ or charged.

These terms are derived from the Greek word elektron, meaning amber. The electricity produced by friction is called frictional electricity. If the charges in a body do not move, then, the frictional electricity is also known as Static Electricity.

Charge is of two types:
Positive charge
Negative charge

Basic properties of electric charge

(i) Quantisation of electric charge

The fundamental unit of electric charge (e) is the charge carried by the electron and its unit is coulomb.  e  has the magnitude 1.6 × 10^−19  C. In nature, the electric charge of any system is always an integral multiple of the least amount of charge. It means that the quantity can take only one of the discrete set of values. The charge,  q = ne  where n  is an integer.

(ii) Conservation of electric charge

Electric charges can neither be created nor destroyed. According to the law of conservation of electric charge, the total charge in an isolated system always remains constant. But the charges can be transferred from one part of the system to another, such that the total charge always remains conserved.

(iii) Additive nature of charge

The total electric charge of a system is equal to the algebraic sum of electric charges located in the system. For example, if two charged bodies of charges +2q,  −5q are brought in contact, the total charge of the system is –3q.

Lightning conductor

This is a simple device used to protect tall buildings from the lightning.

It consists of a long thick copper rod passing through the building to ground. The lower end of the rod is connected to a copper plate buried deeply into the ground. A metal plate with number of spikes is connected to the top end of the copper rod and kept at the top of the building.

When a negatively charged cloud passes over the building, positive charge will be induced on the pointed conductor. The positively charged sharp points will ionize the air in the vicinity. This will partly neutralize the negative charge of the cloud, thereby lowering the potential of the cloud. The negative charges that are attracted to the conductor travels down to the earth. Thereby preventing the lightning stroke from the damage of the building.

Dr. A. P. J. Abdul Kalam

डॉ. ए पीजे. अब्दुल कलाम के 11 सिद्धान्त, जिससे सीखा पूरे देश ने

एक महान विचारक, विद्वान, विज्ञानविद और उच्च कोटी के मनुष्य, भारत के 11वें राष्ट्रपति डॉ. ए. पी. जे. अब्दुल कलाम, एक ख्याती प्राप्त वैज्ञानिक इंजीनियर जिन्होने भारत को उन्नत देशों के समूह में सबसे आगे लाने के लिये प्रक्षेपण यानो तथा मिसाइल प्रऔद्योगिकी के क्षेत्र में उल्लेखनीय योगदान दिया है। अब हमारे बीच नहीं रहे।

Shillong: Former President APJ Abdul Kalam, a popular President between 2002 and 2007, passed away on Monday after he collapsed during a lecture in Shillong.

तमिलनाडु के रामेश्वरम्  में 15 अक्टूबर को जन्में डॉ. अब्दुल कलाम अपनी सफलता का श्रेय सर्वप्रथम अपनी माँ को देते हैं, उनके अनुसार—“मैं अपने बचपन के दिन नही भूल सकता, मेरे बचपन को निखारने में मेरी माँ का विषेश योगदान है। उन्होने मुझे अच्छे-बुरे को समझने की शिक्षा दी। छात्र जीवन के दौरान जब मैं घर-घर अखबार बाँट कर वापस आता था तो माँ के हाँथ का नाश्ता तैयार मिलता। पढाई के प्रति मेरे रुझान को देखते हुए मेरी माँ ने मेरे लिये छोटा सा लैम्प खरीदा था, जिससे मैं रात को 11 बजे तक पढ सकता था। माँ ने अगर साथ न दिया होता तो मैं यहां तक न पहुचता।“

अब्दुल कलाम एक तपस्वी होने के साथ-साथ एक कर्मयोगी भी हैं। अपनी लगन, कङी मेहनत और कार्यप्रणाली के बल पर असफलताओं को झेलते हुए आगे बढते गये। अपनी उपलब्धियों के दम पर आज उनका स्थान अर्न्तराष्ट्रीय वैज्ञानिकों में से एक है।

 प्रारम्भिक जीवन में अभाव के बावजूद वे किस तरह राष्ट्रपति के पद तक पहुँचे ये बात हम सभी के लिये प्रेरणास्पद है। उनकी शालीनता, सादगी और सौम्यता किसी महापुरुष से कम नही है। उनसे मिलने की इच्छा स्वाभाविक है जो हममें से कई लोगों की होगी।। उनके जीवन से हम बहुत प्रभावित हैं। हम उनको अपना आर्दश मानते हैं।

डॉ. कलाम बच्चों तथा युवाओं में बहुत लोकप्रिय हैं। हम सब आदरवश उन्हे मिसाइल मैन कह कर बुलाते हैं। अपने सहयोगियों के प्रति घनिष्ठता एवं प्रेमभाव के लिये कुछ लोग उन्हे ‘वेल्डर ऑफ पिपुल’ भी कहते हैं। परिवारजन तथा बचपन के मित्रजन ‘आजाद’ कह कर पुकारते थे।

डॉ. कलाम के दर्शन सिद्धान्त बेहद प्रभावशाली हैं।

1-  जो लोग जिम्मेदार, सरल, ईमानदार एवं मेहनती होते हैं, उन्हे ईश्वर द्वारा विशेष सम्मान मिलता है। क्योंकि वे इस धरती पर उसकी श्रेष्ठ रचना हैं।

2-  किसी के जीवन में उजाला लाओ।

3-  दूसरों का आर्शिवाद प्राप्त करो, माता-पिता की सेवा करो, बङों तथा शिक्षकों का आदर करो, और अपने देश से प्रेम करो इनके बिना जीवन अर्थहीन है।

4-  देना सबसे उच्च एवं श्रेष्ठ गुणं है, परन्तु उसे पूर्णता देने के लिये उसके साथ क्षमा भी होनी चाहिये।

5-  कम से कम दो गरीब बच्चों को आत्मर्निभर बनाने के लिये उनकी शिक्षा में मदद करो।

6-  सरलता और परिश्रम का मार्ग अपनाओ, जो सफलता का एक मात्र रास्ता है।

7-  प्रकृति से सिखो जहाँ सब कुछ छिपा है।

8-  हमें मुस्कराहट का परिधान जरूर पहनना चाहिये तथा उसे सुरक्षित रखने के लिये हमारी आत्मा को गुणों का परिधान पहनाना चाहिये।

9-  समय, धैर्य तथा प्रकृति, सभी प्रकार की पिङाओं को दूर करने और सभी प्रकार के जख्मो को भरने वाले बेहतर चिकित्सक हैं।

10- अपने जीवन में उच्चतम एवं श्रेष्ठ लक्ष्य रखो और उसे प्राप्त करो।

11- प्रत्येक क्षण रचनात्मकता का क्षण है, उसे व्यर्थ मत करो।

अब्दुल कलाम, सादा जीवन, उच्च विचार तथा कङी मेहनत के उद्देश्य को मानने वाले वो महापुरूष हैं जिन्होने सभी उद्देशों को अपने जीवन में निरंतर जीया भी है। उनका कहना है कि—-

“सपने देखना बेहद जरूरी है, लेकिन सपने देखकर ही उसे हासिल नही किया जा सकता। सबसे ज्यादा जरूरी है जिन्दगी में खुद के लिये कोई लक्ष्य तय करना”

मित्रों, हम सब अगर उपरोक्त बात को समझें और जीवन में उतारें तो अपने अपने लक्ष्य में सफल हो सकते हैं। इसी विश्वास के साथ कलम को विराम देते हैं।

Source:- दैनिक भास्कर

Origin of the universe

Origin of the Universe

The following three theories have been proposed to explain the origin of the Universe(Basic information only):-

(i) Big Bang theory 

According to the big bang theory all matter in the universe was concentrated as a single extremely dense and hot fire ball. An explosion occured about 20 billion years ago and the matter was broken into pieces, thrown off in all directions in the form of galaxies. Due to continuous movement more and more galaxies will go beyond the boundary and will be lost. Consequently, the number of galaxies per unit volume will go on decreasing and ultimately we will have an empty universe.

(ii) Pulsating theory

Some astronomers believe that if the total mass of the universe is more than a certain value, the expansion of the galaxies would be stopped by the gravitational pull. Then the universe may again contract. After it has contracted to a certain critical size, an explosion again occurs. The expansion and contraction repeat after every eight billion years. Thus we may have alternate expansion and contraction giving rise to a pulsating universe.

(iii) Steady state theory

According to this theory, new galaxies are continuously created out of empty space to fill up the gap caused by the galaxies which escape from the observable part of the universe. This theory, therefore suggests that the universe has always appeared as it does today and the rate of expansion has been the same in the past and will remain the same in future. So a steady state has been achieved so that the total number of galaxies in the universe remains constant.

Newton's third law of motion

Newton’s third Law of motion


It is a common observation that when we sit on a chair, our body exerts a downward force on the chair and the chair exerts an upward force on our body. There are two forces resulting from this interaction: a force on the chair and a force on our body. These two forces are called action and reaction forces. Newton’s third law explains the relation between these action forces.

It states that  for every action, there is an equal and opposite reaction. (i.e.) whenever one body exerts a certain force on a second body, the second body exerts an equal and opposite force on the first.

Newton’s third law is sometimes called as the law of action and reaction.

It is to be noted that always the action and reaction do not act on the same body; they always act on different bodies. The action and reaction never cancel each other and the forces always exist in pair. 

The effect of third law of motion can be observed in many activities in our everyday life. The examples are

(i) When a bullet is fired from a gun with a certain force (action), there is an equal and opposite force exerted on the gun in the backward direction (reaction).

(ii) When a man jumps from a boat to the shore, the boat moves away from him. The force he exerts on the boat (action) is responsible for its motion and his motion to the shore is due to the force of reaction exerted by the boat on him.

(iii) The swimmer pushes the water in the backward direction with a certain force (action) and the water pushes the swimmer in the forward direction with an equal and opposite force (reaction).

Newton's second law of motion

Newton’s second law of motion 

Newton’s second law of motion deals with the behaviour of objects on which all existing forces are not balanced.

According to this law,  the rate of change of momentum of a body is directly proportional to the external force applied on it and the change in momentum takes place in the direction of the force.

The force acting on a body is measured by the product of mass of the body and acceleration produced by the force acting on the body.

The second law of motion gives us a measure of the force.

The acceleration produced in the body depends upon the inertia of the body (i.e) greater the inertia, lesser the acceleration.

Newton's first law of motion

Newton’s first law of motion

It states that  every body continues  in its state of rest or of uniform motion along a straight line unless it is compelled by an external force to change that state. This law is based on Galileo’s law of inertia. 

Newton’s first law of motion deals with the basic property of matter called inertia and the definition of force.

 Inertia is that property of a body by virtue of which the body is unable to change its state by itself in the absence of external force.

The inertia is of three types 

(i) Inertia of rest 

It is the inability of the body to change its state of rest by itself.

Examples 

(a) A person standing in a bus falls backward when the bus suddenly starts moving. This is because, the person who is initially at rest continues to be at rest even after the bus has started moving. 

(b) When we hit a cardboard then the coin placed on it fall in the glass and do not move with the cardboard due to inertia of rest.

(c) When a carpet is beaten by a stick, the dust particles fall off vertically downwards once they are released and do not move along the carpet and fall off.

(ii) Inertia of motion
Inertia of motion is the inability of the body to change its state of motion by itself. 

Examples 

(a) When a passenger gets down from a moving bus, he falls down in the direction of the motion of the bus. 

(b) A passenger sitting in a moving car falls forward, when the car stops suddenly. 

(c) An athlete running in a race will continue to run even after reaching the finishing point. 

(iii) Inertia of direction 

It is the inability of the body to change its direction of motion by itself. 

Examples 

When a bus moving along a straight line takes a turn to the right, the passengers are thrown towards left. This is due to inertia which makes the passengers travel along the same straight line, even though the bus has turned towards the right.

This inability of a body to change by itself its state of rest or of uniform motion along a straight line or direction, is known as inertia. The inertia of a body is directly proportional to the mass of the body. 

From the first law, we infer that to change the state of rest or uniform motion, an external agency called, the force is required. 

Force is defined as that which when acting on a body changes or tends to change the state of rest or of uniform motion of the body along a straight line. A force is a push or pull upon an object, resulting the change of state of a body. Whenever there is an interaction between two objects, there is a force acting on each other. When the interaction ceases, the two objects no longer experience a force. Forces exist only as a result of an interaction.

Mind blowing facts of science..

Mind blowing facts of science..

1. The average human body carries ten times more bacterial cells than human cells

It’s funny how we compulsively wash our hands, spray our countertops and grimace when someone sneezes near us—in fact, we do everything we can to avoid unnecessary encounters with the germ world. The truth of the matter is that each and every one of us is a walking petri dish! All the bacteria living inside you would fill a half-gallon jug or 10 times more bacterial cells in your body than human cells, according to Carolyn Bohach, a microbiologist at the University of Idaho. Don’t worry, though. Most of these bacteria are helpful; in fact, we couldn’t survive without them.

For one thing, bacteria produce chemicals that help us harness energy and nutrients from our food. Germ-free rodents have to consume nearly a third more calories than normal rodents to maintain their body weight, and when the same animals were later given a dose of bacteria, their body fat levels spiked, even if they didn’t eat any more than they had before. The gut bacteria is also very important to maintaining immunity.

2. An individual blood cell takes about 60 seconds to make a complete circuit of the body

You have about 5 litres of blood in your body (at least most people do) and the average heart pumps about 70 ml of blood out with each beat. Also, a healthy heart beats around 70 times a minute. So, if you multiply the amount of blood that the heart can pump by the number of beats in a minute, you actually get about 4.9 litres of blood, which is almost your whole body’s worth of blood. In just a minute, the hearts pumps the entire blood volume around your body. (image source)


Source:- zme science

Cornea has no blood vessels

Cornea of human eye has no blood vessel..

The cornea is the eye’s outermost layer. It is the clear, dome-shaped surface that covers the front of the eye.

Unlike most tissues in the body, the cornea contains no blood vessels to nourish or protect it against infection. Instead, the cornea receives its nourishment from the tears and aqueous humor (a fluid in the anterior portion of the eye) that fills the chamber behind it. The cornea must remain transparent to refract light properly, and the presence of even the tiniest blood vessels can interfere with this process. 

The hot chocolate effect

The Hot Chocolate Effect

Have you ever noticed that the sound that you get from a cup of coffee changes as you stir in sugar? See and Listen to the clip below.

Take a CLEAN cup and fill it with cold water from the tap (it MUST be cold) and put it in the microwave for a minute or two. Don't boil it - just bring it up to 70C or so. A good drinking temperature.
Now add a teaspoon of sugar, stirring as you do it. Make sure you use a metal teaspoon. Listen to the tinkling noise it makes. Notice that the pitch drops. Now stop stirring, but keep tapping the outside of the cup. Notice that the pitch rises again?

Explanation:

Air is more soluble in cold water than in hot water. Cold water out of the tap has lots of dissolved air. When you heat it up in the microwave the air-in-water solution becomes supersaturated. Adding sugar (or any granular material) very quickly nucleates lots of tiny air bubbles out of solution.

The note frequency f is equal to the speed v of the wave divided by four times the height of the water column h: 

 The speed of sound in a homogeneous liquid, according to the Newton-Laplace formula: 

Water is approximately 800 times denser than air, and air is approximately 15,000 times more compressible than water. When water is filled with air bubbles, however, the fluid's density is very close to the density of water, but the compressibility will be the compressibility of air. This greatly reduces the speed of sound in the liquid. Wavelength is constant for a given volume of fluid, therefore the frequency (pitch) of the sound will decrease as long as gas bubbles are present.

Upon initial stirring, entrained gas bubbles reduce the speed of sound in the liquid, lowering the frequency. As the bubbles clear, sound travels faster in the liquid and the frequency increases.


Source:http://www2.eng.cam.ac.uk/~hemh/coffeecup/coffeecup.htm
https://en.m.wikipedia.org/wiki/Hot_chocolate_effect

Frost flowers

Frost Flowers

To put it simply, frost flowers are flowers made of frost. More accurately, frost flowers are nothing like that, so let’s put it technically instead: they’re buildups of ice particles around the base of certain plants and types of wood. When the temperature outside the plant is below freezing and the temperature within them is not, then water is pulled to the surface in a process similar to transpiration. This leads to a fragile chain of ice being pushed outward, which ends up forming sprawling, delicate formations. So they’re not exactly flowers—more like leaves, if anything—but they’re just as pretty to look at, and at least twice as cool.

Source:-http://listverse.com/2013/04/28/10-ridiculously-cool-natural-phenomenon/

Check your tv remote using smartphone

स्मार्टफोन से टीवी या अन्य रिमोट को चेक करना
(Check your tv remote using smartphone)

टीवी, स्पीकर, DVD प्लेयर या अन्य किसी डिवाइस का रिमोट जब काम करना बंद कर देता है तो अक्सर बैटरी बदलकर सही होने का पता लगाया जाता है। हालांकि, कई बार बैटरी बदलने से भी बात नहीं बनती। ऐसे में रिमोट ठीक है या नहीं इस बात का पता लगना मुश्किल हो जाता है, लेकिन आपका स्मार्टफोन इस काम को चुटकी में कर सकता है। यानी आप स्मार्टफोन की मदद से इस बात का पता लगा सकते हैं कि रिमोट ठीक है या नहीं।

इसका पता लगाने के लिए रिमोट के सेंसर को फोन के कैमरा के सामने रखकर रिमोट के बटन दबाएं। ऐसा करने पर रिमोट के सेंसर में लाइट ब्लिंक करती नजर आएगी। हालांकि, इसे आप बिना कैमरे की मदद से नहीं देख सकते। यदि सेंसर में लाइट ब्लिंक कर रही है, तो रिमोट पूरी तरह सही है।
( To check your remote, turn on your phone camera and place the sensor of remote in front of your phone camera and press the keys of remote. If you see blinking light in your phone then the remote is ok. This light is not visible to our eyes because we can not see infrared light).

Mind blowing science facts 1

Mind blowing science facts


1. There is enough DNA in an average person’s body to stretch from the sun to Pluto and back. 17 times

The human genome, the genetic code in each human cell, contains 23 DNA molecules each containing from 500 thousand to 2.5 million nucleotide pairs. DNA molecules of this size are 1.7 to 8.5 cm long when uncoiled, or about 5 cm on average. There are about 37 trillion cells in the human body and if you’d uncoil all of the DNA encased in each cell and put them end to end, then these would sum to a total length of 2×10^14 meters or enough for 17 Pluto roundtrips (1.2×10^13 meters/Pluto roundtrip).

2. It can take a photon 40,000 years to travel from the core of sun to surface, but only 8 minutes to travel the rest of way to earth

A photon travels, on average, a particular distance, d, before being briefly absorbed and released by an atom, which scatters it in a new random direction.From the core to the sun’s surface (696,000 kilometers) where it can escape into space, a photon needs to make a huge number of drunken jumps. The calculation is a little tricky, but the conclusion is that a photon takes between many thousands and many millions of years to drunkenly wander to the surface of the Sun. In a way, the light that reaches us today is energy produced maybe millions of years ago. Amazing!

3. When Helium is cooled to almost absolute zero (-460°F or -273°C), the  lowest temperature possible, it becomes a liquid with surprising  properties: it flows against gravity and will start running up and over the lip of a glass container!

We all know helium as a gas for blowing up balloons and making people talk like chipmunks, but what most people don’t know is that it comes in two distinct liquid states, one of which is borderline creepy. When helium is just a few degrees below its boiling point of –452 degrees Fahrenheit (–269 degrees Celsius) it will suddenly be able to do things that other fluids can’t, like dribble through molecule-thin cracks, climb up and over the sides of a dish, and remain motionless when its container is spun. No longer a mere liquid, the helium has become a superfluid—a liquid that flows without friction.

“If you set [down] a cup with a liquid circulating around and you come back 10 minutes later, of course it’s stopped moving,” says John Beamish, an experimental physicist at the University of Alberta in Edmonton. Atoms in the liquid will collide with one another and slow down. “But if you did that with helium at low temperature and came back a million years later,” he says, “it would still be moving.


Source:-http://www.zmescience.com/other/feature-post/10-quick-scientific-facts-will-blow-mind/

Van de Graaff generator

Van de Graaff Generator

Van de Graaff Generator is a linear particle accelerator. In 1929, Robert J. Van de Graaff designed an electrostatic machine which produces large electrostatic potential difference of the order of 10 million volt.

Principle
The working of Van de Graaff generator is based on the principle of electrostatic induction and action of points.

Construction
A hollow metallic sphere A is mounted on insulating pillars. A pulley B is mounted at the centre of the sphere and another pulley C is mounted near the bottom. A belt made of silk moves over the pulleys. The pulley C is driven continuously by an electric motor. Two comb−shaped conductors D and E having number of needles, are mounted near the pulleys. The comb D is maintained at a positive potential of the order of 10 thousands volt by a power supply. The upper comb E is connected to the inner side of the hollow metal sphere.

Working
Because of the high electric field near the comb D, the air gets ionised due to action of points, the negative charges in air move towards the needles and positive charges are repelled on towards the belt. These positive charges stick to the belt, moves up and reaches near the comb E. As a result of electrostatic induction, the comb E acquires negative charge and the sphere acquires positive charge. The acquired positive charge is distributed on the outer surface of the sphere. The high electric field at the comb E ionises the air. Hence, negative charges are repelled to the belt, neutralises the positive charge on the belt before the belt passes over the pulley. Hence the descending belt will be left uncharged. Thus the machine, continuously transfers the positive charge to the sphere. As a result, the potential of the sphere keeps increasing till it attains a limiting value (maximum). After this stage no more charge can be placed on the sphere, it starts leaking to the surrounding due to ionisation of the air.The leakage of charge from the sphere can be reduced by enclosing it in a gas filled steel chamber at a very high pressure.
The high voltage produced in this generator can be used to accelerate positive ions (protons, deuteron)

Applications

It is used as an particle accelerator to generate energetic particle and x-ray beams in fields such as nuclear medicine, treatment of cancer and nuclear disintegration.

If a person insulated from the ground touches the sphere of a Van de Graaff generator, his or her body can be brought to a high electric potential. The hair acquires a net positive charge, and each strand is repelled by all the others. The result is a scene such as that depicted in the photograph. 

Coriolis effects

Coriolis Effects

In physics, the Coriolis effect is a deflection of moving objects when the motion is described relative to a rotating reference frame. In a reference frame with clockwise rotation, the deflection is to the left of the motion of the object; in one with counter-clockwise rotation, the deflection is to the right.

Due to the relatively large size of planet, its motion is not directly felt by humans. However, the Earth’s clockwise rotation causes objects travelling in the Northern hemisphere to be deflected in a gentle clockwise direction in what is known as the Coriolis Force. As the Earth’s surface moves at a different rate relative to the atmosphere, a discrepancy between the rotation of the Earth’s and the movement of the atmosphere causes an object heading towards the north to pick up the energy of the Earth’s rotation, and begin to curve to the east. The opposite occurs in the southern hemisphere. As a result, navigation systems must compensate for the Coriolis Force to avoid deviation to the right or left of the target.

In the inertial frame of reference (upper part of the picture), the black ball moves in a straight line. However, the observer (red dot) who is standing in the rotating/non-inertial frame of reference (lower part of the picture) sees the object as following a curved path due to the Coriolis and centrifugal forces present in this frame.

Object moving frictionlessly over the surface of a very shallow parabolic dish. The object has been released in such a way that it follows an elliptical trajectory.
Left: The inertial point of view.
Right: The co-rotating point of view.


Source:- Wikipedia

Do physics proves the existence of ghosts..

Physics Proves the Existence of Ghosts?

Do Einstein’s Laws Prove Ghosts Exist?

… Despite years of efforts by ghost hunters on TV and in real life, we still do not have good proof that ghosts are real. Many ghost hunters believe that strong support for the existence of ghosts can be found in modern physics. Specifically, that Albert Einstein, one of the greatest scientific minds of all time, offered a scientific basis for the reality of ghosts. …

Now hold on a minute.  As we’ve seen before, it is not uncommon for pseudoscientists and cranks of all kinds to try glomming onto Einstein’s coat-tails as one of the most well-known and respected scientists of the 20th century as a way of trying to gain traction for their ideas.  It is as if they think that by simply invoking Einstein’s name and theories, despite the fact that they have no real understanding of those theories, that it will somehow, magically make them correct.  Of course, this simply displays a fundamental flaw in the thinking of ghost-hunters, because it shows they have no real knowledge of how science (much less physics) works.

Specifically, in this case the ghost-hunters are claiming that Einstein’s theory of relativity “proves” the existence of ghosts:

… For example, ghost researcher John Kachuba, in his book “Ghosthunters” (2007, New Page Books), writes, “Einstein proved that all the energy of the universe is constant and that it can neither be created nor destroyed. … So what happens to that energy when we die? If it cannot be destroyed, it must then, according to Dr. Einstein, be transformed into another form of energy. What is that new energy? … Could we call that new creation a ghost?”

This idea shows up — and is presented as evidence for ghosts — on virtually all ghost-themed websites as well. For example, a group called Tri County Paranormal states, “Albert Einstein said that energy cannot be created or destroyed, it can only change from one form to another. When we are alive, we have electrical energy in our bodies. … What happens to the electricity that was in our body, causing our heart to beat and making our breathing possible? There is no easy answer to that.” … [emphasis added]

Actually, the answer is pretty easy, as long as you understand how energy is related to matter as outlined in Einstein’s theory.  It can all be summed up in what is probably the most well-known, but one of the least understood, equations in all of science…

E = mc^2

… also known as the mass-energy equivalence formula. The equation basically states that matter is a form of energy, and it quantifies the amount of energy bound up in a certain amount of matter (if you want to calculate it, E stands for energy in Joules, m is mass in kilograms, and c is the speed of light – equal to about 300,000,000 meters/second).  We know this formula is an accurate representation of reality because we have performed numerous experiments where matter is annihilated into pure energy (and vice versa), which confirms this equation.  Not to mention, we have technology – such as nuclear power plants and PET scans – which operates based upon the physics summed up in this equation.

So when the ghost-hunters are talking about the “energy” of a person going off into some ethereal realm to form a ghost, I think they are simply making stuff up and abusing Einstein’s famous equation.  That’s because when someone dies, the matter (i.e. energy) forming the person’s body is simply redistributed when they decay away into the environment.  I like the way that Ben Radford puts it:

… After a person dies, the energy in his or her body goes where all organisms’ energy goes after death: into the environment. When a human dies, the energy stored in his or her body is released in the form of heat, and transferred into the animals that eat us (i.e., wild animals if we are left unburied, or worms and bacteria if we are interred), and the plants that absorb us. If we are cremated, the energy in our bodies is released in the form of heat and light.

When we eat dead plants and animals, we are consuming their energy and converting it for our own use. Food is metabolized when digested, and chemical reactions release the energy the animal needs to live, move, reproduce, etc. That energy does not exist in the form of a glowing, ghostly ball of electromagnetic energy, but rather in the form of heat and chemical energy.

Many ghost hunters say they can detect the electric fields created by ghosts. And while it’s true that the metabolic processes of humans and other organisms actually do generate very low-level electrical currents, these are no longer generated once the organism dies. Because the source of the energy stops, the electrical current stops — just as a light bulb turns off when you switch off the electricity running to it. …

Let’s think about it this way: if ghost-hunters were correct that a spiritual realm indeed exists and is populated by the “energy” given off by someone when they die (that is, ghosts being a manifestation of this “energy”), then this poses some pretty sticky questions for the ghost-hunters.  First, how much “energy” does it take to make a ghost?  And, in relation to this question, exactly how much matter from a dead body must be somehow annihilated to form this mysterious “ghost energy”, since we know that mass and energy are interchangeable?  And if, by some miracle, ghost-hunters actually are able to somehow quantify either of the above questions (they haven’t), do they have any way to empirically prove that 1) such a transfer of matter into pure energy indeed takes place and 2) provide an explanation for a physical mechanism which would facilitate such an transfer?

Not to mention, there are other problems.  For instance, if people keep dying and this keeps on generating ghosts and disembodied spirits formed out of “energy” which previously existed in the form of living beings, then eventually would we not have some kind of massive “energy crisis” with too much energy supposedly filling up the spiritual realm at the expense of the physical world?  And if this spirit world really is populated by “ghost energy”, wouldn’t all of the supposed interactions between ghosts and the physical world be generating a helluva lot of entropy, speeding up the onset of the heat death of the universe?!  Wow, and I thought dealing with the future production and distribution of oil was problematic!

In conclusion, it seems clear to me that when ghost-hunters try to talk physics, they just end up looking stupid.  They have nothing even closely resembling a coherent theory, they have no consistent protocols, they have no solid definitions (just try asking one of them to provide a clear-cut definition of a “ghost”!)  What they do have is over-active imaginations and over-blown stories which they think is all that is necessary to do science.  And science just doesn’t work that way.


Source:-https://skepticalteacher.wordpress.com/2011/11/24/physics-proves-the-existence-of-ghosts/

Significant figures

Significant figures

The digits which tell us the number of units we are reasonably sure of having counted in making a measurement are called significant figures. Or in other words,  the number of meaningful digits in a number is called the number of significant figures.

A choice of change of different units does not change the number of significant digits or figures in a measurement.

For example, 2.868 cm has four significant figures. But in different units, the same can be written as 0.02868 m or 28.68 mm or 28680 µm. All these numbers have the same four significant figures.

From the above example, we have the following rules.
i) All the non−zero digits in a number are significant.
ii) All the zeroes between two non−zeroes digits are significant, irrespective of the decimal point.
iii)  If the number is less than 1, the zeroes on the right of decimal point but to the left of the first non−zero digit are not significant. (In 0. 02868 the underlined zeroes are not significant).
iv)  The zeroes at the end without a decimal point are not significant. (In 23080  µm, the trailing zero is not significant).
v) The trailing zeroes in a number with a decimal point are significant. (The number 0.07100 has four significant digits).

Examples
i) 30700 has three significant figures.
ii) 132.73 has five significant figures.
iii) 0.00345 has three and
iv) 40.00 has four significant figures.

How to become invisible

How to make things invisible 
(CLOAKING DEVICES)....

Rapidly developing technology is turning the strangest science fiction plots into science facts. We only see objects when light bounces off of them, producing an image with a range of wave lengths. Scientists have long theorized that objects could be rendered invisible by disrupting the way light interacts with them. If light can be deflected around an object, it could become invisible to the human eye.

Recently, theory became reality when scientists produced a clear hexagonal prism that deflected light around any object inside of it. When placed in an aquarium, the prism caused a goldfish swimming into it to become invisible, while a land based cloak caused farm animals to vanish from site. The scrambling effect works according to the same principles that make stealth aircraft “invisible” to radar.

Atmospheric pressure

Atmospheric pressure

Atmospheric pressure is the pressure exerted by the weight of air in the atmosphere of Earth (or another planet).
You are currently being pressed on from above by 1,000 kilograms of air, the equivalent of the weight of a small car. This is because the Earth’s atmosphere is actually quite heavy, and humans stand at the bottom of an ocean of air carrying an atmospheric pressure of 14.7 pounds per square inch. We are adapted to withstand this pressure, and avoid being crushed by absorbing equally pressurized air into our bodies. However, impermeable objects such as plastic bottles released at altitude are crushed by the time they reach the Earth’s surface.

This plastic bottle was sealed at approximately 14,000 feet (4,300 m) altitude, and was crushed by the increase in atmospheric pressure —at 9,000 feet (2,700 m) and 1,000 feet (300 m)— as it was brought down towards sea level.

As altitude increases, there is less overlying atmospheric mass, so that atmospheric pressure decreases with increasing elevation.

Hot water freezes faster than cold water

Heat Induced Freezing 

Water is the most important liquid on Earth. It’s is also one of the most mysterious and counterintuitive compounds in nature. One of water’s lesser known property, for example, is that hot water freezes faster than cold water. It is not fully understood why, but the phenomenon, known as the Mpemba effect, was originally discovered by Aristotle over 3,000 years ago. The mysterious effect has been attributed to a range of phenomena, but it remains a
mystery.